Hair products for reducing the curl and frizziness of hair have been commercially available for over fifty years for people who want less curly and more manageable hair. Such products are also known as hair straightening or relaxing products and are generally composed of a strong hydroxide base compound that breaks the bonds in the hair in order to straighten or relax curly/kinky hair. There are primarily four different types of alkaline metal hydroxide hair straighteners in use: calcium hydroxide, lithium hydroxide, sodium hydroxide, and potassium hydroxide. The straightening or relaxing product is usually applied quickly and can only remain on the hair for a very limited amount of time because the alkalinity of such products, if not rinsed from the hair at the appropriate time, can damage the hair, as well as cause chemical burns to the scalp and areas surrounding the hair.
Other straightening or relaxing formulations use guanidinium hydroxide which can be formed from the reaction of guanidine carbonate and a very small amount of soluble hydroxide such as calcium hydroxide. The reaction between these two compounds leads to the formation of guanidinium hydroxide and calcium carbonate, which precipitates in the composition. While such a system may provide a better relaxing efficacy and better skin tolerance, the calcium carbonate precipitate makes the final rinsing of the hair much more difficult, and leaves on the hair and the scalp, mineral particles that give the hair a coarse feel and an unattractive appearance resembling dandruff.
Another known permanent hair straightener or reshaping technology employs reducing agents such as thighlycolic acid and cysteine technologies as well as non thiol-based reducing agents such as sulfites and bisulfites which permanently reduce hair bonds. Still other hair relaxing or straightening compositions and processes involve the use of protein denaturants in combination with heat. Protein denaturants are compounds which cause a reversible unfolding of a protein. However, many of the proposed compositions contain formalin, formalin derivatives or formaldehyde-generating compounds, which are known to break down to formaldehyde with high heat, such as during flat ironing of the hair. Formaldehyde fumes generated owing to the break down have been found to cause headaches, respiratory, eye, and mucous membrane irritations, respiratory illnesses, cancer, or even death. Thus, these compositions pose significant safety concerns.
In order to address the concerns mentioned above, other compositions and processes have been proposed, such as those that involve the application of compositions containing non-hydroxide bases and/or protein denaturants that are of the non-formalin or non-formalin derivative types or which do not generate formaldehyde, including pre-washing the hair with high pH compositions. However, there still exists a need to improve such methods and compositions that are just as safe, and which are able to provide greater and longer lasting curl pattern reduction and frizz control, more effective straightening of hair, increased manageability of hair, while minimizing damage to the hair. At the same time, less hair treatment or processing times to achieve these attributes are highly desirable.
Thus, there is an ongoing need and desire to provide a composition and process for effectively straightening or reducing the curl and/or frizziness of hair in an efficient and safe manner while imparting other cosmetic and functional benefits to the hair.